Parking guide system which displays parking guide line on image corrected using homography and method for controlling the same

A method for controlling a parking guide system, comprising:

• photographing, by a camera mounted on a vehicle, images of a rearward direction of the vehicle;
• receiving, by circuitry including a microprocessor, a first image before travelling of the vehicle from the camera;
• determining, by the circuitry, whether an obstacle is detected at a rear side of the vehicle;
• measuring, by a travelling detecting sensor, a travelling distance and a travelling direction of the vehicle when it is determined that the obstacle is not detected;
• receiving, by the circuitry, a second image after the travelling of the vehicle from the camera;
• extracting and matching, by the circuitry, characteristic points commonly included in the first image and the second image;
• calculating, by the circuitry, a first homography, between a first virtual image having a randomly designated characteristic point therein and a second virtual image having the randomly designated characteristic point being virtually moved by a calculation based on the measured travelling information, based on camera parameter information and travelling information of the vehicle;
• calculating, by the circuitry, a second homography, that is a homography between the first image having the extracted characteristic points therein and the second image having the characteristic points therein, based on coordinates of the matched characteristic points;
• comparing, by the circuitry, the first homography and the second homography and determining whether an error exists between the first and second homographies;
• calculating, by the circuitry, a third homography, that is a homography between the first homography and the second homography, for correcting an image photographed by the camera, when the error exists between the first and second homographies, based on a result of a comparison of the first homography and the second homography;
• and
• displaying, by the circuitry, a parking guide line on the corrected image to which the third homography is applied by means of a display device mounted on the vehicle.